HUBS L18 Flashcards
How does a chemical signal get converted into an electrical signal?
Neurotransmitter binds → Opens chemically-gated ion channels.
Ions flow → Voltage changes in a localized membrane area.
Threshold reached (-60mV at axon hillock) → Action potential starts.
Gated ion channels are opened by a stimulus
How do chemically-gated ion channels open and close?
Neurotransmitter binds → Channel opens.
Channel changes shape → Allows ion flow.
Ions move → Follow electrochemical gradient.
Neurotransmitter unbinds → Channel closes.
How do voltage-gated ion channels open and close?
Membrane depolarizes → Reaches threshold (e.g. -60mV).
Channel opens → Shape changes.
Ions move → Follow electrochemical gradient.
Membrane potential shifts → Channel inactivates or closes.
Axon hillock, gated ion channel
Voltage-gated
Na+ and K+
channels
Axon, gated ion channel
Voltage-gated
Na+ and K+
channels
Axon terminals
Voltage-gated
Ca2+
channels
At rest, the intracellular space has more negative charge than the
extracellular space, creating an “electrical gradient”:
Resting Membrane Potential
Local potentials are a change in voltage (charge)
in a specific area of the cell
EPSP?
EPSP = Excitatory Post-Synaptic Potential (an excitatory local potential).
How do EPSPs form?
Presynaptic neuron releases excitatory neurotransmitter (e.g., ACh).
Neurotransmitter binds → Opens chemically-gated Na⁺ channels.
Na⁺ enters post-synaptic cell → Causes depolarization (membrane becomes more positive/+)
What is an IPSP?
Inhibitory Post-Synaptic Potential (an inhibitory local potential).
How do IPSPs form?
Presynaptic neuron releases inhibitory neurotransmitter (e.g., GABA).
Neurotransmitter binds → Opens chemically-gated K⁺ or Cl⁻ channels.
K⁺ exits or Cl⁻ enters → Causes hyperpolarization (membrane becomes more negative/-).
What is a local potential? At what part of a neuron does it occur?
An excitatory or inhibitory change in voltage
What are excitatory local potentials?
Excitatory local potentials, or EPSPs (Excitatory Post-Synaptic Potentials), are small, temporary increases in membrane voltage caused by excitatory neurotransmitters. They occur when a presynaptic neuron releases neurotransmitters like acetylcholine (ACh), which bind to chemically-gated Na⁺ channels, allowing Na⁺ to enter the post-synaptic cell. This depolarizes the membrane (makes it more positive), bringing it closer to the threshold needed to trigger an action potential.
What are inhibitory local potentials?
